1. Field of the Invention
This invention relates to a fluid cylinder assembly incorporating load transducers (as defined hereinafter) for detecting the thrust exerted by a piston rod.
2. Description of the Prior Art
The prior art fluid cylinder assembly is useful for various purposes such as subjecting a component part of a machine to press fit, clamping, chucking, roller pressure or stamping. According to the purpose for which the fluid cylinder assembly is used, it is necessary to detect the magnitude of thrust exerted by a piston rod or the magnitude of load acting on the component part.
For example, when a component part of a machine is subjected to press fit, force exerted thereon is measured with a view to using the measured value for passing a judgment on whether or not the component part has been properly subjected to press fit.
It is known to measure such force by means of a load cell carried either on the outer end of the piston rod (as disclosed in Japanese Utility Model Registration No. 2,569,871) or on a cap cover secured on the end of a cylinder tube opposite the end at which the piston rod is extendible and retractable.
The load cell carried on the outer end of the piston rod assures that the results of measurement are obtained with a high degree of accuracy, because the magnitude of load acting on the component part can be directly measured. The trouble is that a lead wire extending outwardly of the load cell moves as the piston rod moves. Therefore, a supporting member or members have to be employed as a means to movably support the lead wire and prevent it from being disconnected.
In case of the load cell carried on the cap cover, the output taken from the load cell contains not only the magnitude of load acting on the component part but also the magnitude of gravity acting on the fluid cylinder assembly per se. Especially when the fluid cylinder assembly is mounted on a vertical supporting structure in cantilever fashion, i.e., with the cap cover allowed to support the gross weight of the fluid cylinder assembly, the output taken from the load cell contains not only the magnitude of thrust acting on the component part but also the magnitude of angular moment acting on the fluid cylinder assembly per se. A marked decline in the accuracy of measurement results therefrom.